The present invention relates to a mercury sphygmomanometer. More particularly, the present invention pertains to a mercury sphygmomanometer which is capable of being housed in a casing.
FIG. 6 is a partially-sectioned schematic view showing a conventional mercury sphygmomanometer.
Referring to FIG. 6, a mercury passage 1 is connected to a mercury reservoir 2 through a communicating tube 3. The tube 3 is provided with a cock 4 which is opened and closed by means of a handle 5.
A cuff, or wrapping sleeve, 6 is connected to the mercury reservoir 2 through a tube 7 and also connected to a bulb 9 through a tube 8. The mercury passage 1 is provided at its upper end with a filter 10 and a small bore 11 through which the mercury passage 1 is communicated with the outside air. The reference numeral 12 denotes mercury.
In actual use, the cuff 6 is wrapped around the arm and, with the cock 4 opened, air is pumped into the cuff 6 by means of the bulb 9. In consequence, the mercury 12 in the mercury reservoir 2 rises through the mercury passage 1, thus enabling measurement of blood pressure.
After use, the mercury passage 1 is tilted to return all the mercury remaining in the passage 1 to the mercury reservoir 2 and then the cock 4 is closed in order to prevent leakage and contamination of the mercury 12.
There is another type of conventional mercury sphygmomanometer having an arrangement in which a cover is formed together with the mercury passage in one unit so that, as the cover is closed, the cock is automatically closed.
Of the above-described conventional apparatuses, the former, that is, the prior art wherein mercury is returned by tilting the mercury passage, has the disadvantage that the cock must be opened and closed every time the apparatus is used. Further, if the sphygmomanometer is moved with the cock left opened because the operator forgot to close it, a contaminative substance in the mercury reservoir may enter the mercury passage and adhere to the wall thereof, resulting in the mercury passage being stained.
There is also a fear of the mercury column becoming discontinuous; in such a case, air enters the space between the separated portions of the mercury column, thus causing adverse effects on the measuring accuracy. To remove the air, the mercury passage must be tapped or swung.
The latter, that is, the prior art wherein the cock is automatically opened and closed in response to an operation of opening and closing the cover, has the disadvantage that mercury is not completely returned to the mercury reservoir when the cover is closed.